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Users have asked many times how to add a podcast by url. The only non-answer was this: https://community.spotify.com/t5/Closed-Ideas/Podcasts-Searching-for-particular-Podcast/idi-p/153199...
All other answers to this question simply point to this non-answer. That's pathetic. If Spotify can't provide basic customer service, then I'm going to ditch it.
This applies to using Spotify on all devices - premium version or otherwise.